The present invention relates to surgical clip instruments and, in particular, to surgical instruments for removing polymeric hemostatic clips.
Various types of hemostatic and aneurysm clips are used in surgery for ligating blood vessels to stop the flow of blood. Moreover such clips may be used for interrupting or occluding ducts and vessels in particular surgeries such as sterilization procedures. Generally, the clips are left in place until hemostasis or occlusion occurs.
Two types of clips, metal and plastic, have been preferred. Metal clips of alloys of stainless steel, titanium and tantalum are generally U-shaped or V-shaped. By means of a dedicated applier, the clip is permanently deformed over the vessel. An example of one such clip is disclosed in U.S. Pat. No. 5,509,920 to Phillips et al. An example of a metallic clip applied is disclosed in U.S. Pat. No. 3,326,216 to Wood wherein a forceps-type applier having conformal jaws is used to grip and maintain alignment of the clip during deformation. Such appliers may additionally dispense of plurality of clips for sequential application as disclosed in U.S. Pat. No. 4,509,518 to McGarry et al.
With the advent of high technology diagnostic techniques using computer tomography (CATSCAN) and magnetic resonance (MRI), metallic clips were found to interfere with the imaging techniques. To overcome such interference limitations, biocompatible polymers have been increasing used for surgical clips. Inasmuch as the plastic clip cannot be permanently deformed for secure closure, latching mechanisms have been incorporated into the clip design to establish closure conditions and secure against vessel opening. A particularly strong and secure plastic clip is disclosed in U.S. Pat. No. 5,062,846 to Oh et al. and assigned to the assignee of the present invention. Therein the plastic clip comprises a pair of curved legs joined at their proximal ends with an integral hinge and carrying at their distal ends interlocking latching members. Exemplary appliers for installing such clips are disclosed in U.S. Pat. No. 5,100,416 to Oh et al. and assigned to the assignee of the present invention. Therein, the distal ends of the clip include lateral bosses that are engaged by the jaws of the applier. Upon closure, the legs are pivoted inwardly about the hinge and contact and deflect the hook to allow reception of the locking tab.
While substantial advances have been made by the above and other approaches in the prior art for installing metal and polymeric clips, such instruments are solely dedicated to application and cannot be reversely operated to remove the clip once applied. Certain tools have been used for reversely deforming and removing metallic clips. However, a satisfactory instrument for removing latching polymeric clips has not been available. In instances where a surgeon desired to remove or relocate the clip, heretofore, the clip had to be physically severed by appropriate cutting instruments, such as scalpels, scissors and the like. Such removal techniques require substantial time and dexterity to remove safely the clip without adverse consequences to surrounding tissue. Accordingly, it would be desirable to provide a surgical instrument for removing plastic latching clips in a manner that releases the clip from a latched condition in a single piece without destruction of the clip and damage to surrounding tissue.
In view of the foregoing limitations, it is an object of the present invention to provide an effective instrument for removing polymeric surgical clips from a latched condition at the surgical site without physical destruction thereof.
Another object of the invention is to provide a surgical clip removal instrument for polymeric latching clips using non-destructive techniques and the inherent characteristics of the clip to achieve a released state at the surgical site for removal of the clip in a single piece.
A further object of the inventions is to provide a forceps-type surgical clip removal instrument that can be operated with simple closure movement to unlatch two-legged polymeric hemostatic clips directly at the surgical site.
The foregoing objects and other advantages are achieved in the present invention by a surgical clip removal instrument having operative surfaces at the distal jaws that directly compress the legs of a latched surgical clip and upon limited closure movement differentially elongate the clip legs to achieve an unlatched condition. Upon release of the jaws, the inherent resiliency of the clip outwardly biases the legs while maintaining contact with the jaws, allowing the surgeon to remove the clip from the surgical site through withdrawal of the instrument thereby eliminating supplemental retrieval techniques and instruments.
More particularly, the removal instrument is of the forceps-type having a pair of elongated pivotal handles terminating with distal jaws. The instrument includes stop surfaces defining an open position and a closed position. The jaws have a stepped configuration including abutting surfaces adjacent the pivotal connection prescribing the closed position. Outwardly of the stop surfaces, the jaws terminate with low friction planar clip engaging surfaces lying in planes parallel to and spaced from the pivotal axis of the handles to establish a controlled width transverse gap. A cantilevered spring connected between the handles biases the jaws and through a slot and stop pin connection limits opening of the jaws in the normally open position. To remove a latched clip the jaws of the instrument are positioned to overly longitudinally the legs of the clip. Upon closing movement, the outer leg of the clip is flattened by one jaw increasing the longitudinal length thereof. At the opposed jaw, the clip hinge and latching hook are contacted and upon corresponding closure, the hinge and latching hook slide apart without changing the length of the other leg, gradually withdrawing the inner leg from the latched condition at the hook. After achieving an unlatched condition, further opening of the jaws allows the inherent resiliency at the hinge to outwardly pivot the legs to a fully released condition allowing removal of the clip in a single piece from the surgical site. Critical to the effective operation of the removal instrument is the aforementioned jaw spacing. If the gap is too wide in comparison with the latched height of the clip, the clip will not be sufficiently compressed to achieve the necessary differential leg lengths for unlatching. On the other hand, if the gap is too narrow, both legs will be compressively engaged precluding relative movement of the legs. Further, the planar jaws must have relatively low frictional characteristics for accommodating the necessary relative movements of the legs to the unlatched condition.